Rupintrivir is a peptide aldehyde that targets the human rhinovirus (HRV) 3C proteinase enzyme and has the potential for the treatment of the common cold. Rupintrivir is derived from AG-6084 - in order to develop human rhinovirus 3C protease inhibitors with improved pharmacological properties, Agouron replaced the backbone amide moiety of the series which yielded AG-6084, with a ketomethylene isostere. A phase II efficacy study has been completed in healthy patients infected with the rhinovirus. Ruprintrivir was well tolerated; blood-tinged mucus and nasal passage irritation were the most common adverse effects reported. Pharmacokinetic analysis of plasma and nasal ruprintrivir concentrations revealed intranasal drug residence with minimal systemic absorption. The fact that rupintrivir is active against noroviruses belonging to genogroup I (Norwalk virus), genogroup V (murine norovirus), and the recombinant 3C-like protease of a GII norovirus suggests that the drug exerts cross-genotypic anti-norovirus activity and will thus most likely be effective against the clinically relevant human norovirus strains. Rupintrivir is also a high affinity inhibitor of Enterovirus-71 3C protease.